Elucidation of the mechanisms which control food intake in normal and obese monkeys is theprimary focus of this research project. The normal feeding behavior and metabolic profile of primates will be defined, together with the effects of different feeding schedules and dietary compositions on body weight, adiposity, total intake, and metabolic pathways. Models of human obesity will be developed through overfeeding, lesioning, and genetic selection using Macaca mulatta and Macaca nemistrina. These models will be compared to each other and to normal monkeys for cues to critical differences in regulatory mechanisms and behavior. Finally, recognizing that complex interactions of both hormones and fuel substances probably underlie the regulation of intake and body composition, a large number of potential signals will be studied simultaneously under varied conditions including cross circulation, intravenous, and intraarterial infusions.